Cellulosic fibers are multi-component structures made from cellulose polymers, i.e. cellulose chains. Lignin, pentosans, hemicelluloses and other components known in art may also be present. The cellulose chains in the fibers are attached to each other to form elementary fibrils. Several elementary fibrils are bound to each other to form microfibrils and several microfibrils form aggregates. The links between the cellulose chains, elementary- and microfibrils are hydrogen bonds.
Microfibrillated cellulose (MFC) (also known as nanocellulose) is a material made from wood cellulose fibers, agricultural raw materials or waste products, where the individual microfibrils have been partly or totally detached from each other. Other raw materials can also be used to produce nano or microfibrils. MFC is normally very thin (˜20 nm) and the length is often between 100 nm to 10 μm. However, the microfibrils may also be longer, for example between 10-100 μm but lengths up to 200 μm can also be used. Fibers that has been fibrillated and which have microfibrils on the surface and microfibrils that are separated and located in a water phase of a slurry are included in the definition MFC.
MFC can be produced in a number of different ways. It is possible to mechanically treat cellulosic fibers so that microfibrils are formed. However, it is very energy consuming method to for example shred or refine the fibers and it is therefore not often used without combining the treatment with a pre- or post-treatment.
One example of production of MFC is described in WO2007091942. In the method described in WO20070912942, the MFC is produced by the aid of refining in combination with addition of an enzyme.
However, there is still a need for an improved process for the production of MFC.